as always interested in your real life experience: what size for the low pressure fuel line (tank to pump) do you guys have installed to provide for a 500HP motor? any disadvantages in not running a vapor return line? THX, Ralf
According to the instructions, for engines over 450 HP, you should use 1/2" (-8AN) from tank to pump. If you do not use the vapor return feature the pump will make 1 psi more pressure, about 8 psi. With it installed, it will make about 7 psi. https://www.robbmcperformance.com/products/buick550.html My CV products pump makes 8-9 psi and I have occasionally seen 10 psi. My Q-jet and AED carburetors don't seem to mind one bit.
Mine makes about 9 psi at idle, Qjet was fine with it. Drops to about 6 psi under WOT feeding 586 hp. Video:
Thanks guys! @ Larry: Jim mentioned the CV pump, but I am a little shy due to the price tag. W/ or w/o vapor return line W/ or w/o vapor return line and what size pick up line? I am in need of a little education here: In what mode of operation is the thirst of the motor the highest? At high engine rpm, close to peak HP, or thru out the whole rpm range, at WOT?
Have the RobbMc 550 on the Riv's 430. With the 3/8 line it would starve for fuel around 4500 RPM. Pulled and modified the sender to 1/2" Ran 1/2" hard line all the way to the front of the car and reused the stock 3/8 as return. Have not had an issue again.
Ralf i run stock return line its always at 7 lbs and over at idle. I had a stage 1 pump with stock line half way thru 2nd it nosed over changed to RobbMc pump 1/2" sender 1/2" line to the pump It pulls hard now
At WOT, at highest engine load, at highest RPM, in other words, at the top end of the track on a 1/4 mile pass.
Vapor return line is capped off. Pick up line is 1/2". Pump flow falls off as rpms climb, but fuel demand increases
Dumb question: when you say you ran 1/2 inch line, did you replace the entire factory fuel line from the tank to the fuel pump?
Thats what I am going to do. To me it does not make sense to have a 1/2" pickup and to still restrict the flow/volume by keeping the stock 3/8" fuel line. At a given pressure in a line, there is more volume/time flow, the bigger the diameter is. And given the length from tank to pump, the low pressure line is quite a restrictor in the system.
I did just that. If ya look close you can see the copper line run from a filter in front of the R R wheel well all the way up to behind the RF wheel. The rubber 1/2 line goes into a factory hole in the frame, up through a clip in the spring pocket, through the cross member out another hole and into the pump. So it is true 1/2" all the way from the bottom of the tank. Could not find a sock for the pick up so its made longer towards the back and put a metal filter in line
It's easy enough to leave the factory lines in place and run a new line. I ran a braided 1/2" line for the feed and repurposed the factory 3/8" line as my return line. The original return line is still in place unused. I added the robb mc 1/2" sender while I was there..
I may be replacing my 3/8 factory feed line, so I was looking for options. My return is 6an, running Holley Blue Pump on rear frame rail. RobbMC sending unit, 8an stainless to 3/8 hardline . I used Aeroquip push-lock for my transmission lines that I ran through the frame and had intended to use it for fuel feed line. Then I came across this, https://ls1tech.com/forums/fueling-...socketless-hose-fc598-anyone-else-issues.html I may just go with stainless 6an. I don't feel as though my 450-500hp requires 8an...Jim
Joe, that is exactly what I will do. What level of pain was it to route the braided line? Did you route it close along the stock lines? I already have purchased Dash 10 PTFE steelbraided line, as this is close to 1/2" inner diameter. Outer diameter is 0.64" and I hope it will feed thru the openings of the frame.
I ran my -8AN push lok through the frame. It really wasn't bad. I have a word document on running the line, that I got from Jim Weise that I can't post here, but I can e mail it.